Process for producing polyester polyols with low quantities of dioxane waste

Abstract

The present invention relates to the production and use of polyester polyols produced from at least one aromatic dicarboxylic acid or an alkyl ester of an aromatic dicarboxylic acid or the anhydride of an aromatic dicarboxylic acid and at least one α,ω-diol, wherein the formation of 1,4-dioxane from diethylene glycol is largely suppressed by means of specific reaction management.

1 . A one-step process for producing polyester polyols, comprising:
 a) mixing
 (A) at least one compound selected from the group consisting of aromatic dicarboxylic acids, alkyl esters of aromatic dicarboxylic acids, and anhydrides of aromatic dicarboxylic acids, 
 and 
 (B) at least one α,ω-diol, 
   thereby forming a polyester polyol, wherein the molar ratio of components (B) to (A) is in the range of 20:1 to 1.05:1 and the proportion by weight of components (A) and (B) in total, based on the total weight of the mixture obtained in step c), is in the range of between 55 and 99 wt. %, and   b) adding (C) phthalic anhydride to the polyester polyol obtained in step a), in a molar ratio of components (C) to (A) added in step a) in the range of 0:1 to 2:1, thereby forming a polyester polyol, and   c) adding (D) diethylene glycol to the polyester polyol obtained in step b), in a proportion by weight of 1 to 35 wt. %, based on the total weight of the mixture, thereby forming of a polyester polyol,   wherein the polyester polyol obtained in step b) has a higher molecular weight than the polyester polyol obtained in step c).   
     
     
         2 . The process according to  claim 1 , wherein (A) said compound is an the aromatic dicarboxylic acid selected from the group consisting of phthalic acid, tercphthalic acid, isophthalic acid and mixtures thereof. 
     
     
         3 . The process according to  claim 1 , wherein (B) said α,ω-diol is selected from the group consisting of ethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol and higher homologs thereof with number-average molecular weights of 150 to 410 g/mol. 
     
     
         4 . The process according to  claim 1 , wherein the molar ratio of components (B):(A) is in the range of 1.1:1.0 to 10.0:1.0. 
     
     
         5 . The process according to  claim 1 , wherein the molecular weight of the polyester polyol obtained from step a) is in the range of between 4000 and 2000. 
     
     
         6 . The process according to  claim 1 , wherein the OH number of the polyester polyol obtained from step a) is in the range of between 28 and 560 KOH/kg. 
     
     
         7 . The process according to  claim 1 , wherein the molecular weight of the polyester polyol obtained from step b) is in the range of between 4500 and 600. 
     
     
         8 . The process according to  claim 1 , wherein the OH number of the polyester polyol obtained from step b) is in the range of between 25 and 190 g KOH/kg. 
     
     
         9 . The process according to  claim 1 , wherein the viscosity of the polyester polyol obtained from step b) at a temperature of 25° C. is in the range of between 400 and 20000 mPas. 
     
     
         10 . The process according to  claim 1 , wherein the proportion by weight of components (A) and (B) in total, based on the total weight of the mixture, is in the range of between 60 and 90 wt. %. 
     
     
         11 . A polyester polyol obtainable according to the process of  claim 1 . 
     
     
         12 . A process for producing a polyurethane foam, which may optionally contain polyisocyanurate groups, which comprises reacting
 a) a polyester polyol is produced by the process of  claim 1 ,   with   b) at least one polyisocyanate-containing component, in the presence of   c) one or more blowing agents,   d) one or more catalysts,   and, optionally, in the presence of   d) one or more flame retardants and other auxiliary substances and additives, and, optionally, with   at least one compound having at least two isocyanate-reactive groups, which differs from said polyester polyol a).   
     
     
         13 . A polyurethane loam, which may optionally contain polyisocyanurate groups, produced by the process according to  claim 12 . 
     
     
         14 . (canceled)